iPads will no longer connect to studio computer via UC Surface

I have a single studio computer that is connected to a Studio 192 on it.  I have an iPad (OSX version 9.3.5) that is running the latest version of UC Surface (2.5.0.45267) that used to connect just fine to the studio computer, but has recently stopped connecting.  When I start the app on the iPad, it shows the studio computer (and the correct IP address) as a possible connection, but when I tap it, nothing happens.  I tried installing UC Surface same version to a new iPad (running OSX 11.2.1) and the exact same thing happens.

I have verified that Universal Control is allowed thru my firewall, as well as verifid that the PresonuseHardwareAccessService.exe is also allowed thru the firewall, and I have also verified that UDP port 47809 is allowed thru the firewall.  The studio computer's UC Surface software connects fine and I can control the mixer and all functions from the local computer, but not from remotes and this used to work.  I have followed what (very) scant troubleshooting information is available on this and a few other boards, but nothing works.  It's not a deal-breaker, but I really do like have the UC Surface running on the iPad for quick changes to settings as well as being able to control the talkback mike.

There have been no updates to software here, either the OS or anything else.  I can verify that.

Anyone got any ideas here?  I'm truly stumped- I'm very well versed in networking, and really don't want to go thru a "please dump your settings/reboot your computer" kind of troubleshooting, because I've already done all of that about 35,312 times already.  HELP!!!

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